Electromagnetic switch



Sept.23, 1958 H. J. scAGNELLl ET AL 2,853,577

ELECTROMAGNETIC SWITCH sepuzs, 1958 H. J. SCAGNELLI ET AL 2,853,577

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NNN 58% Sept- 23, 1958 H. J. cAGNELLl ET AL 2,853,577

ELECTROMAGNETIC SWITCH Filed May 19, 1954 4 Sheets-Sheet 5 //4I W 22 /fjlrgvlg/ /ff 54 ce/ l l i f |57 SePt- 23, 1958 H. J. scAGNELLl ET AL 2,853,577

ELECTROMAGNETIC SWITCH Filed May' 19, 1954 4 Sheets-Sheet 4 United States Patent O ELECTROMAGNETIC SWITCH Henry J. Scagneili, Bronx, and John H. Landsiedel,

Mamaroneck, N. Y., assignors to Ward Electric Company, a corporation of New York Application May 19, 1954, Serial No. 430,784 8 Claims. l(Cl. 20G-104) This invention relates to electromagnetically operated switches and particularly to the actuating mechanism interconnecting the actuating solenoid and the movable contact. The invention is further directed' to the contactor head and the casing housing the solenoid and actuating mechanism and supporting the contactor head.

In various uses of contact devices such as switches, relays or the like it is often desirable or necessary to have a contact device that will withstand shock. Such devices 'remain in either a closed contact position or an open position when shock or a heavy blow is applied to the device -1n any directlon and also are easily changed from closed to open position or from open to closed position when specifically actuated. The Vremote or automatic control of the switches or the like makes it necessary that they be operated by an electrical device, such as a solenoid which does not permit the vlocking of the switch by latches. vThe operation of the circuit makes it undesirable to have with a minimum of operating parts.

Another object of the invention is to provide an electromagnetic switch that is symmetrical about all center lines of three mutually perpendicular planes.

Another object of the invention is to provide an electromagnetic switch that is compact and with a minimum of operating parts.

Another object is to provide a shockproof-electromag,

netic switch that is simple in construction and inexpensive to manufacture.

Other and further objects of the invention will be apparent from the following specification taken in connection with the drawings in which:

Fig. 1 is a side View of the switch with the side cover removed to show the actuating mechanism;

Fig. 2 is an end view of the switch with a partial sectional view along lines 2-2 of Fig. l including the side cover; f

Fig. 3 is a sectional View of the switch taken along lines 3-3 of Fig. 2; l

Fig. 4 is Aa sectional View of the switch taken along lines 4-4 of Fig. 1 including the end cover;

Fig. 5 is a sectional view of the switch taken along lines Fig. 6 is a side view of the switch with the end cover removed and'showing the actuating means in acontact engaging position;

Fig. 7 is a fragmentary sectional view of the counterweight; and

Fig. 8 is a top view of the movable contactor head and the fixed contactor heads without the end support.

Referring to Fig. 4, an electromagnetically operated switch is shown. The switch comprises a solenoid 10 operating a movable contactor head 13 above the solenoid by means of a set of four-bar linkages 11 and 12 (Fig. 2) on each side of the solenoid. The solenoid is mounted between side frames 20 and 21 housing the four-bar linkages 11 and 12 respectively. The side frames transversely support the fixed contact heads 1S and 19 (Figs. l and 3) on each side of the movable contactor head 13.

In Fig. 6 the side frame 20 is rectangular'and has anges 26, 27, 28, 29, 30 around the edges thereof. The cover 22 is. secured to the side frame 20 by bolts 32 threaded in the weld nuts 33 which are welded to the side frame 20 (Fig. 2). The weld nuts are cylindrical, with an internal threaded bore extending axially through each Weld nut, and engage the indents 34 to space the cover from the side frame 20 to form an enclosure for housing the four-bar linkage and associated operative elements.

The side frame 21 is of similar construction with anges 38, 39, 40, 41, 42 around the edges of the rectangular side frame 21 (Fig. l).

In Fig. 2 the cover 23 is shown securely fastened to the side frame 21 by bolts 47 threaded into the weld nut 48, similar to weld nut 33, which is welded to the frame 21. The indents 49 are seated against the weld nuts to space the cover from the side frame to form an enclosure housing the four-bar linkage 12 (Fig. 2 or 4). Thus the cover 22 and side frame 20 are held a precise distance apart and the cover 23 and side frame 21 are similarly held a precise distance apart so that the covers and side frames guide and hold the linkages 11, 12 and associatively connected mechanism in the proper operative relationship as described in detail later herein. The bolts 32 and 47 permit the easy removal of the covers 22, 23 for access to the operating mechanism and assembly of the parts.

In Fig. 6 the fixed contactor heads 18 and 19, positioned transversely across the two side frames, are secured to side frames 20 and 21 by long bolts 35 extending through the multiple section contactor heads 18, 19 respectively and are threaded in rivnuts 37 secured to the flanges 26, 30, 38 and 42.

In Figs. 3 and 4 the solenoid 10 is supported by U- shaped casing or saddle 50 having the walls 51, 52, 53 forming a U-shape and mounted between the side frames 20, 21 by projections 54, 55, in Fig. l, on the edges of the wall fitting into staggered rectangular slots 56, 57 arranged in a staggered U-shaped row in the respective side frames 20, 21. Thel U-shaped casing 5'0 is positioned between the side frames 20 and 21 and during the assembly of the switch the projections 54, 5S are aligned with the slots 56, 57 respectively. The side frames are then forced together to engage the edges of the Walls 51, 52, 53. Thus the casing or saddle 50 provides a spacing means for the side frames 20 and 21. In Figs. 2 and 3 a removable end cover 60 forms a fourth wall to the casing 5t) and has projections 61 tting into slots in the top wall 51 and is secured by a bolt 62 to the wall 53. At the bottom of the switch are mounting plates 58, 59 having projections 43, 44 fitting into openings 45, 46 in the side frames 20, 21. Rivet nuts 63 are secured to the ilanges 28, 40 (Figs. 1 and 6) and are for mounting on the back of a board. The mounting plates 58, 59 are for mounting on the front of a board. The side frames 20, 21 are held together by alternately bending the projections 54, 55 over against the side frames 20, 21.

The solenoid has two U-shaped opposing armatures 65, 66 slideably mounted in upper and lower rail guides or channels 67, 63 (Figs. 2 and 3). The guides are preferably made of non-magnetic material. The rail guides extend through the rectangular openings in the cover 60 and opposite wall 52 of the casing 50. The lower guide 68 sets on the lower edge of the opening and the upper edge 67 rests on the insets closing the openings in the cover 60 and wall 52 against the armatures. extend beyond the cover 60 and wall 52 to form a continuous sliding surface through the electromagnet and projecting at both sides. Tabs 70, 71 are punched from the central wall of the rails and bend substantially perpendicular to the guides 67, 68 respectively. Bolts 72, 73 with lock washers are fitted into openings in the tabs 70, 71 respectively and threaded into the cover 60 to securely hold the guides from longitudinal movement. Thus the rail guides in which the armatures reciprocate are rigidly held against vibration and movement.

In Figs. 3 and 4 the coils 74, 75 of the solenoid 10 are wound to fit on the rail guides 67, 68 and the legs 76, 77 of armature 65 and legs 78, 79 of armature 66. The coils produce separate electromagnetic fields and electromagnetic forces of substantially equal intensity to draw the armature 65, 66 in evenly along the guides. An insulator 81 and a curved leaf spring 82 are pressed in the space between the end of the coils and the cover to longitudinally anchor the coils against movement on application of the magnetizing current. The insulator and spring are shaped like a figure eight with holes through which the legs 76, 77 move. The solenoid may be preassembled and placed inside the saddle shaped casing 50 after which the insulator and the leaf spring with the cover 60 are positioned. The rail guides 67, 68 are then inserted. The cover 60 may then be closed tight and secured with the bolt 62. The bolts 72, 73 are threaded in place.

The armatures 65 and 66 are made of U-shaped steel laminations stacked to form legs 76, 77 and 78, 79 respectively. On each side of the armatures 65, 66 are metal U-shaped standards 101, 102 and 103, 104 (Fig. 5) respectively. These standards serve to support the armatures and form part of the electromagnetic path. The laminations are held together by rivets 83, S4 (Fig. 3) in armatures 65, 66 respectively. The cover 60 and wall 52 have ribs 86, 87 respectively to increase the strength and rigidity. The ribs 87 provide a passage for the wires 88 connecting the coils to a source of electricity.

The shafts 90, 91 extend preferably through the midpoint of the central legs 92, 93 of the armatures 65, 66 to exert a balanced resistance to the actuation of the armatures as shown in Fig. 5. The shafts 90, 91 are connected to diagonally `opposite ends of the linkages 11, 12 to impart a balanced actuating force to the linkages. In the covers 22, 23 are elongated indents 94, 95 holding the shaft in place. Elongated slots 96, 97, 98, 99 are provided in the side frames 20, 21 to pass the shafts 90 and 91 in the side frames 20, 21.

On energization of the solenoid the armatures 65, 66 are drawn into the solenoid and the shafts 90, 91 slide in slots 96, 97, 98, 99 and along the indents 94, 95.

Current is supplied to the coils 74, 75, which form a part of the preassembledv solenoid, through the wires 88 and draws the armatures 65, 66 towards each other. The actuation of the armatures is transmitted to the linkage mechanism by the shafts 90, 91 which move in opposite directions towards each other squeezing the linkage mechanism along the diagonal between the two shafts, as shown in Fig. 6.

The linkage mechanism 11 comprises four links 108, 109, 110, 111 with the links 109, 111 having two bars. The links 108, 110 fit in between the bars and are pivotally fastened together by flanged sleeves 112, 113, 114, 115 pivotally fitting through holes in the links. The single bar link 108 and the double bar link 109 are connected by the flanged sleeve 112 and turn about the axis of the sleeve. The double bar 109 is similarly connected at the other end of the single bar link 110 by the flanged sleeve The guides 113. The single bar fits in between the two bars of link 111 both pivotally fastened together by flanged sleeve 114. Similarly, the double bar 111 and single bar 108 are attached by the flanged sleeve 115. Each of the linksis flexibly connected at each end so that the links form a parallelogram pivoted at each corner. The links are pret erably of the same length with the center of the holes spaced the same distance apart for each link. The links, however, may be made of other than equal lengths with corresponding modifications in the associated parts of the switch. The shafts 90 and 91 rotatably fit into the diagonally opposite flanged sleeves 113 and 115 respectively so that the links freely rotate about the sleeves and shafts. The diagonally opposite sleeves 112, 114 are mounted on pins or studs 117, 118 which slide in elongated slots 120, 121 and 122, 123 in the side frame 20 and cover 22 rcspectively. The slots 120, 122 are opposed and coincide. The ends of the pin or stud 117 tit in the slots and the sides of the slot guide the pin in a linear movement. The pin or stud 118 is similarly positioned in the slots 121, 123.

in Fig. l, a side view of the linkage mechanism 12 between side frame 21 and cover 23 is shown. The mechanism 12 is identical to linkage mechanism 11. It operates in the identical manner and exerts on the movable contactor head 13 a balance actuating force of the same magnitude and duration as the linkage 'mechanism The two mechanisms raise or lower the head 13 at the same time so that engagement of the contacts is substantially simultaneous. The links 126, 128 have double bars and links 125, 127 have single bars. Flanged sleeve 129 pivotally interconnects links 125 and 126, and flanged sleeves 130, 131, 132 similarly join the pairs of links 126, 127, 128, 125, respectively to form a parallelogram with sides of equal length and pivotally connected. The diagonally opposed sleeves 132, are journaled on the shafts 90, 91 which pass through the armatures 65, 66 and are similarly journaled in the flanged sleeves 113, 115 of linkage mechanism 11 in Fig. 6.

Pins or studs 134, 135 rotatably lit in the flanged sleeves 129, 131 respectively, and slideably set in the pairs of longitudinally aligned elongated slots 136, 137 and 138, 139 in the side frame 21 and cover 23.

The movable contactor head 13 is supported between two flat actuating members 141, 142 with right angle flanges at the upper end receiving the long bolts 143, 144 fastening the actuating members by means of nuts or tapped holes 145, 146 to the actuating members. The actuating member 141 extends into the enclosure of the side frame 20 parallel to the movement of the linkage mechanism, and the actuating member 142 extends into the enclosure of the side frame 21 parallel to the movement of the linkage mechanism 12. The actuating member extends nearly the entire length of the side frame 20 and is secured at the upper end to the pin 117 to be moved up and down on the actuation of the linkage mechanism. The flanged sleeve 112 and shoulder 147 of pin 117 hold the actuating member against substantial axial movement along the pin by slideably engaging the edges of the turned bosses 122, 120, respectively. The actuating member 141 is guided in linear movement by shoulder pin 117 which is guided by flanged sleeves 120 and 122 and by pin 118 which is respectively guided by flanged sleeves 121 and 123. Pin 118 slideably engages the wall 150 forming an elongated opening at the end of the actuating member 141.

In the side frame 21, the actuating member 142 is similarly secured to and actuated by the linkage mechanism 12. The pin 134 fits in a complementary hole to actuate the member up and down. The shoulder 151 of pin 134 and sleeve 129 hold the actuating member 142 against substantial axial movement by slideably engagng the edges of the turned bosses, and space the actuating member 142 from the boss around the opening `136 in 'a similar manner to that by which the counteryweight plate 157 spaces the actuating member from the yisguided by flanged sleeves 136, 137 andby pin 135` which is guided by flanged sleeves 138, 139.

Thus the movable contactor head 13 moves linearly and is evenly spaced between the fixed heads 18, 19

during actuation and return strokes.

Counterweights 156, 157 are provided to counterbalance the inertia of the movable contactor head 13. The weights are secured to the lower pins 118, 135 respectively, and have walls 158, 159 in the counterweight plates 160, 161 forming elongated slots above the pins 118, 135. The pins 148, 152 engage the Walls 158, 159 to guide the slot in a linear movement opposite in direction to that of the actuating members 141, 142. The counterweights 156, 157 havea generally'triangular shape with truncated corners. Considering the counterweight 157 in Fig. l, the counterweight plate 161 has weights 164, 165 spaced from one another toA provide a passage for the actuating member 142 and positioned below the links 127, 128 with sloped surfaces or edges 166, 167 to conform to the angle of rest of the links. This arrangement reduces the vertical space required by thelinkage mechanism and the counterweight while maintaining the thickness `of the side frame 21 at a minimum value. The generally triangular shape permits a generally triangular arrangement of guide projections to engage cover 23 and side frame 21 to maintain the motion `of the counterweight parallel to the linkage mechanism. The' weights 164, 165 have a thickness that is less than the width of the enclosure so that the weight is spaced from the cover and plate. The rounded ends of pins 169, 170 at opposite lower corners of the counterweight are in slideable engagement with the cover 23, andthe spaced dents 171, 172 at the upper apex (Fig. 5) are in slideable contact with the side frame 21 to prevent the tipping and turning of the counterweight. As best illustrated in the-fragmentary sectional view of the counterweight in Fig. 7, the pin 169 is seated in a dent 169:! engaging the side frame 21. The counterweight is thus positioned between and spaced from the side frame and cover. Thus, on one side the counterweight is held in a linearly slideable position by rounded' projections at the lower endsl and by two rounded projections at the apex. On the other side thecounterweight is held by the actuating member 142 which bears against the flanged collars 129,

` 131. The counterweight is'prevented from tipping endwise by a stationary pin 152 slideably fitting in a slot formed by wall 153 in the counterlweightiplate. The bolts 47 threadedin theweld nuts 48 slideably clamp the linkage mechanism 12, actuating member `142 and counterweight in substantially parallel movements. The dent on the other side from'the pins such a's 169 is not clearly illustrated in the other figures of the drawing and will be described herein inferentially. In the disengaging position the elongated slot formed by the walll '159 in the counterweight plate 1'61'is above the counterweight stationary pin 152, and the elongated slot formed by the wall 153 in the actuatingmernber is below the pin .152, thereby reducing the height of the side frame 21 by permitting guide pin 152 to extend through both slots. The elongated slots then overlap in theengaging position, as illustrated in'Fig. 6.

The counterweight 156 is identical with counterweight 157 and has weights 174, 175 in the opposite lower corners forming a passageway for the actuating member 141. In Fig. 6, the linkage mechanism 11 is shown in the actuation or raised position andthe counterweight 156 in the lowermost position. With the linkage mechanism 11 in a distended or raised 'position and the counter- 6 frame 20 is utilized. The fixed pin 148 is in the lower'- mostl portion of the opening in the wall 149. The 'pins v176, 177 at the opposite corners of the counterweight engage the cover 22, and the dents 178, 179 at the apex engage the side frame 20 to hold the counterweight from twisting and turning on movement, in cooperation with dents on the side frame 20 of the counterweight similar `to dents 169a illustrated in Fig. 7. The counterweights could be replaced by a second movable contactor head at the opposite end of the actuating members 141, 142 to counterbalance the movable head 13.

lt is thus seen that the movable contactor head 13 is actuatably supported at each end by the actuating mechanism. The movement of the armatures 65, 66 of the solenoid is along a center line at right angles to the movement of the movable contactor head, and that of the armatures is between the two actuating mechanisms 11 and 12. The armatures 65, 66 are connected by shafts 91, 92 to` diagonally opposite corners of thelinkage mechanisms 11 and 12 and on actuation move towards each other to separate the pins at the other corners and actuate the movable contactor head 13. The movable 'contactor head 13 remains in contact with the fixed contacts as long as the solenoid is energized. One deenergization the movable contacts if above the actuating mechanism will drop. However, springs 181, 182 are provided between the vertical diagonals of the mechanisms 11 and 12 to draw pins 117, 118 and 134, 135 together and force the armatures 65, 66 apart. The flanged bearings, such as bearing 113 connecting links 109, 110, serve to hold the links together. They also serve as spacers so that the linkage mechanisms 11 and 12 are each an integral member. In addition, the flanged bearings position the linkage mechanisms between the respective covers and side frames and provide a bearing surface for the links.

The movable contactor head 13 comprises three molded insulating blocks 185, 186, 187 stacked with intertting surfaces and held together as an integral member by the long bolts 143, 144 and nuts or tapped recesses 145, 146 which also fasten the blocks as a unit on top of the actuating members 141, 142. The actuating members move the head 13 up and down between the fixed heads 18, 19. As shown in Fig. 8, head 18 has rounded guides 188 fitting in the rounded grooves 189. The head 19 has rounded guides 190 fitting in grooves 191. The guides 188, 190 preferably extend the height of heads 18, 19 to guide the movable contactor head 13 through the distance of travel ofthe heads 18, 19. The grooves 189, 191 similarly extend the height of head 13. The guides and grooves hold the movable head from sidewise movement.

The movable contactor head 13 as described in this preferred embodiment carries two sets of contacts to match the two sets of contacts in head 18 and the two sets of contacts in head 19. Contacts-192, 193 comprise one set and are clamped between blocks 185, 186. The other set of contacts 194, 195 are held between blocks 186, 187. The contacts extend from both sides of the movable contact head 13 to engage two sets of fixed vcontacts in head 18 and two sets of fixed contacts in head 19. In Fig. 8 a top view of the upper sets of conlower set is shown. Considering Fig. 8, the splitter type contacts 192, 193 extend from both sides of the head 13 with contact 192 having contacting blades 192a, 192b fittingbetween the fingers of the fixed contacts 196, 197 respectively and the contacting blades 193a, 193b contacting the opposing fixed contacts 198, 199 respectively. The lower sets of contacts are similar except that the setsof fixed and movable contacts have buttons as shown in Fig. 3 where the movable contact 195 has `button contacts engaging the fixed contacts 200, 201.

Referring to Fig. 4, the blocks 186, 187 are shown of similar construction with intertting keys andV notches to align the holes through which the bolts 143, 144 pass and the holes in which the pins 203, 204, 205, 206 t. The pins 203, 204, 20S, 206 securely hold the contacts 192, 193, 194, 195 respectively from lateral movement and in line with the contacting portion of the iixed contacts. Considering more specifically the movable contacts, the contact 195 shown in Fig. 3 is resiliently held along the direction of `movement of the head 13 by a helical spring 208 to permit play in the movable head 13 without separating the contacting surface of the fixed 'contacts 200, 201. Contact 194 has a similar spring 207. For a similar reason the contact 192 has blade contacts 192:1, 192b with the width of the blade in the same direction as the movement of the movable head 13. The head may move down slightly from a contacting position and the blades 1920, 192b and buttons 195a, 1951) will remain in contact with the fixed contacts 196, 197 and 200, 201 respectively. The splitter type contacts 192, 193 may be replaced by button type contacts and the button type contacts may be replaced by the splitter type. The button contacts that are spring supported are interchangeable with the splitter type contacts and vice versa.

Another'modilication that may be made is that the fixed contactor heads may be inverted and the movement of movable contactor head 13 would be reversed with the contacts out of engagement when the solenoid is energized.

Spaces or grooves 209, 210 are provided through which the contacts 194, 195 move. A block 211, 212 is iitted in similar grooves in blocks 186 to rigidly -hold thecontacts 192, 193. The fixed contactor heads 18, 19 each comprise two lixed molded insulating blocks 216, 218 and 219, 220 of similar construction. In Fig. 8 the upper blocks 216, 219 have contactor chambers 221, 222 and the lower blocks have chambers 223, 224 with chambers 221, 223 facing chambers 222, 224. The contacting portions of the ixed contacts are positioned in these chambers, and terminal grooves 225, 226, 227, 228 carry the terminal straps 230, 231, 232, 233 to the cable clamps or terminals 234, 235, 236, 237. The contacts 195A, 195B are representative of the lower contacting sets with the contacts 200, 201 in the upper positions of -chambers 223, 224 to provide for the travel of contact 195. The chambers, such as 223, 224 having button contacts, are provided with U-shaped metallic shields 241, 242 to provide on interruption of the circuit a magnetically conductive path to establish a self induced magnetic field creating a blow-out action on an arc between the oontacts. An end support 243 is fastened to the fixed contactor heads 18, 1.9 to cover the upper sets of contacts and the movable head.

It is thus seen that a novel and more advantageous type of electromagentic switch is described above. The actuating mechanisms 11 and 12 coupling the solenoid 10 with the movable contactor head 13 prevent the movement of the head on application of a force to the switch. If the switch is in a closed position the contacts remain closed in a current carrying condition and if the contacts are open they remain open. The mounting of the linkage mechanisms, the counterweight, and actuating member in a side by side slideable arrangement provides a compact arrangement of the actuating parts so that the parts may be mounted in a narrow or at enclosure formed by the side frames 20, 21. The solenoid is placed between the side frames and the contactor head is connected across the side frames above the solenoid providing a strong contactor that can support high current carrying contacts and terminals well insulated from one another and from grounds outside of the switch. The size of the actuating parts and the arrangement of the contactor head and solenoid provide an electromagnetic switch that is small in size and has a high current and voltage rating and in addition is shockproof and operable in any position. The counterweight balances the movable contactor so that if the switch is turned with the solenoid above the contactor, the force actuating the movable contactor or returning the contactor is the same in any position.

Another advantage obtained is the ease of access to the actuating parts and the assembly of the parts. The actuating parts are readily exposed by removing the cover of the side frame. The cover in addition to protecting the actuating parts serves as a retaining member to hold the linkage mechanism on the pins land shafts. The actuating parts may be connected together without using bolts and nuts by sliding the members together.

The end of the casing S0 has a cover 60 normally closing the opening inside of the saddle. The coils may be removed from the casing without unlocking any fasteuings except the removal of the bolts 62. The shaft 91 is easily removed by taking o either of the covers 22, 23 and sliding the shaft out. lt is thus seen that all the parts of the switch are readily accessible and easily assembled or removed.

Other advantages appear in the foregoing description. The above described invention is also applicable to relays, contactors, interlocks and the like and it is not intended to limit the invention to switches. Modifications and changes may be made and adaptations to relays and contactors and the like may be made without departing from the scope of the invention as set forth in the appended claims.

We claim:

l. An electromagnetic switch capable of maintaining a desired setting under shock conditions comprising a linkage mechanism having two sets of pivotal pins movable in straight lines at right angles to one another, a freely movable contactor head and a freely movable counterweight connected to opposite pins of a set, and a pair of oppositely and freely movable armatures each connected to opposite pins of the other set so that shock movement of said switch in any plane will create equal and opposite forces on each pin of the other diagonal to hold the switch in a set position.

2. An electromagnetic switch capable of withstanding shock comprising a fixed contactor head, a movable contactor head actuatable in and out of engagement with said fixed contactor head along a linear movement, a solenoid having two armatures of substantially equal weight linearly movable in opposite directions and similarly responsive to equal actuating forces, a counterweight having a weight equalto said movable contactor head, a linkage mechanism having four bars of substantially equal length 'and four pins pivotally interconnecting said bars to form a parallelogram with two sets of diagonally opposite pins movable at right angles to one another, said armatures being separately connected to respective pins of one set of diagonally opposite pins and said counterweight and said movable contactor head being connected to respective pins of the other set of diagonally opposite pins so that shock movement of said switch plane of said linkage will create equal and opposite forces on each pin of the other diagonal to hold said linkage mechanism and said movable contactor head in a set position.

3. An electromagnetic switch capable of withstanding shock comprising a Xed contactor head, a movable contactor head actuatable in and out of engagement with said xed contactor head `along a linear movement, a solenoid having two armatures of equal Weight linearly movable in opposite directions, a counterweight having a weight substantially equal to said movable contactor head, a linkage mechanism having four bars and cylindrical pins, ea-ch bar having a pair of circular holes with the centers of the holes of each bar equal distances apart, each pin tting in only two holes on different bars to pivotally interconnect said bars and form the bars into a parallelogram having sides of equal length, a plate having two sets of elongated slots with the longitudinal lengths of each set at right angles, each of the slots being substantially equal in length and having a width to guide a respective pin in slideable engagement, said armatures being separately connected to one set of diagonally opposite pins and said counterweight being separably connected to the other set of diagonally opposite pins so that shock movement of said switch in any plane will create equal and opposite forces on each pin of the other diagonal to hold said linkage mechanism `and movable Contact in a set position.

4. An electromagnetic switch comprising a 'Fixed contactor head, a movable contactor head, a four-bar linkage mechanism having two sets of pins movable in straight lines at right angles to one another for actuating said movable contactor member in and out of engagement with said fixed contactor member, a frame supporting said iixed contactor head and having two plates on opposite sides of said linkage mechanism, said plates each having a set of elongated slots opposing one another, a set of said pins tting into a set of said slots to guide the motion of said linkage mechanism, means for actuating said linkage mechanism connected to one set of pins, and counterbalancing means and said movable contactor head connected to said other set of pins to be actuated by said actuating means through said four-bar linkage mechanism.

5. An electromagnetic switch comprising an actuating linkage mechanism having four bars pivotally interconnected by four pins each extending through two of said bars to form a parallelogram, an actuating member secured to one of said pins and having a guide slot in which the diagonally opposing pin slides, a counterbalancing means connected to the pin diagonally opposing the pin connected to said actuating member, a frame having two plates spaced to form an enclosure housing said bars, said actuating member and said counterbalancing means, said plates each having a set of elongated openings face to face to guide said pins in a linear movement, said plates holding said bars, said counterbalancing means, and said actuating member in longitudinally slideable arrangement, said actuating member and said counterbalancing means longitudinally moving in opposite directions on actuation of said bars.

6. An electromagnetic switch comprising a lixed contactor head, a movable contactor head actuatable in and out of engagement with said fixed contactor head, a linkage mechanism having two sets of pivot connections diagonal to one another, one set connected to said movable contactor head and the other set connected to said solenoid comprising a pair of U-shaped balanced armatures connected to opposite pivot connections of the other set, each of said armatures having a pair of legs, two coils, each coil having one leg of each armature alected thereby, a casing around said armature with end walls having openings, runners or rail guides extending through 10 said openings and said coils, said armatures slideably mounted in said runners and drawn into said coil to actuate said movable contact, and resilient means connected to said linkage mechanism to return the movable head out of contact with said fixed contact and said armatures out of said coil.

7. An electromagnetic switch lcomprising two actuating mechanisms, a solenoid for actuating said mechanisms, side frames spaced from one another by said solenoid and each housing a respective actuating mechanism, two contact heads spaced from one another and connected across said spaced side frames, a movable contactor head positioned between said spaced contact heads and actuatably supported by said actuating mechanisms housed in said side frames and operated by said solenoid through said actuating mechanisms.

8. A switch comprising 'frame means, two spaced xed contactor heads of insulating material mounted on said frame means and with each head having a plurality of recesses therein, and a movable contactor head of insulating material between said fixed contactor heads forming a closing wall when in engaging position, said movable contactor head having a plurality of contacts each extending through said movable contactor for projecting into a respective recess, said fixed contactor heads having a fixed contact in each recess engageable by a respective projecting portion of the movable contact for completing the circuit across said movable contactor head, said frame means having guide means with slots and actuating means with pins litting in said slots, two

actuating members connected at opposite ends of the movable contactor head and projecting in the direction of movement of said movable contactor head to overlap with said frame means and engage said guide means to prevent endwise movement of said movable contact head and to receive said pins and connect said actuating means and said actuating member to linearly guide said actuating member and movable contact head by movement of the pins in said slots ou engagement and disengagement of said xed and movable contacts.

References Cited in the tile of this patent UNITED STATES PATENTS 1,701,440 Chatto Feb. 5, 1929 2,356,039 Ellis et al. Aug. 15, 1944 2,444,157 Dries June 29, 1948 2,474,742 Kuhn lune 28, 1949 2,489,185 Johnson Nov. 22, 1949 2,492,762 Palme Dec. 27, 1949 2,513,934 Hall luly 4, 1950 2,534,069 Schleicher Dec. 12, 1950 2,672,536 Rosing et al. Mar. 16, 1954 2,758,167 Weide Aug. 7, 1956 UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patentv Ncb 2,853,577 September 23, 1958 Henry J Seagnelli et an,

` t is' hereby certified that error appears in the above numbered patent requiring correction and that the said Letters' Patent Should read as eor= ree'te'd below In the grant, line-e:V 2. and 3,v and line l22 in the heading to thev printed specification, lines' A and 5j name' of assignee, for 'Ward Electric Company"7 each occurrence, read fm Ward Leonard. Eleetrie Company mer,

Signed and sealed this' 14th day of July 195% Attest:

KARL IL AXLI E A N ROBERT C. WATSON Attes'ting Officer Conmissioner of Patents UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent Na. ,2,853,577 september- 23, 1958 Henry Jha Soagnelli et al.

It 'LS hereby certified that error appears in the above numbered patent requiring correction and that the 'said Letters' Patent 'should read as oor== reote'd below.,

In the grant; lines. 2 yand 3,- and line l2', in the heading to the printed specification, lines' fand 5;., name of assignee, for "Ward Electric' Company"y each occurrence, read am Ward Leonard Eleotrio4 Company me Signed and sealed this' 14th day of July 1959.,

l (Smm Attest:

KARL H. AXLINE I ROBERT c. WATSON A'bbeSting Officer Commissioner of Patents 

